Xenon acne drug misses efficacy endpoints in phase 2

Xenon's stock price crashed following news of the blow to XEN801

A phase 2 trial of Xenon Pharmaceuticals’ acne candidate XEN801 has missed its primary and key secondary efficacy endpoints. The comprehensive failure prompted Xenon to admit the data don’t support continued development of XEN801 and wiped 44% off its stock price in premarket trading.

Xenon enrolled 165 patients with moderate-to-severe facial acne and randomized them to receive either a gel formulation of XEN801 or placebo. After 12 weeks in which participants applied a gel to their faces each evening, investigators looked for changes against baseline. The study’s primary endpoint was the percent change in lesion count after 12 weeks. Secondary endpoints looked at lesion counts after four and eight weeks, and the change on an investigator assessment scale.

Management at Xenon thought small molecule SCD1 inhibitor XEN801 could improve outcomes by reducing the size and number of sebaceous glands, but the data fell well short of expectations. XEN801 failed to outperform placebo against the primary efficacy endpoint. And it came up short against “key secondary efficacy endpoints.”

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Faced with a clean sweep of negative efficacy endpoints, Xenon CEO Simon Pimstone, M.D., Ph.D. held his hands up and admitted it looks like the end of the line for XEN801.

“Despite the good scientific and preclinical rationale to pursue SCD1 as a novel acne target, the topline clinical results do not support this hypothesis or the continued development of XEN801,” Pimstone said in a statement.

The setback leaves Xenon looking to a preclinical asset targeting rare forms of severe childhood epilepsy and its partnered programs for near-term boosts. Xenon expects to file an IND for the in-house asset, XEN901, in the fourth quarter, by when it should have learnt how Teva-partnered pain drug TV-45070 has fared in its phase 2b. TV-45070 failed a phase 2b trial in osteoarthritis pain in 2015, ramping up the pressure on the upcoming readout in post-herpetic neuralgia.

Xenon expects Genentech, another of its partners, to move one of its pain programs into phase 2 later this year. But the failure of XEN801 nonetheless leaves Xenon’s pipeline a little light. The company plans to remedy this by adding ion channel modulators through in-house research and dealmaking. Xenon had $64.1 million in cash as of the end of last year.

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